In general, ethylene-vinyl alcohol copolymer (hereinafter, referred to as EVOH, and EVOH is obtained by hydrolyzing of a copolymer of a vinyl ester monomer and ethylene.) is excellent in transparency, gas barrier properties, aroma retention, solvent resistance, oil resistance and the like, and, with such properties, has been used for various packaging materials such as a food packaging material, a pharmaceutical packaging material, an industrial chemical packaging material and an agricultural chemical packaging material. The EVOH materials are often subjected to thermal stretching treatment for the purposes of compatibility with the shape of the applied container and the improvement of mechanical strength and the like. Further, in recent years, multilayer stretched films containing EVOH are used widely and thus, the velocities of film forming and stretching tend to be increased to improve productivity thereof.
In such high-speed film forming and high-speed stretching, an EVOH which has further improved stretching properties and an EVOH superior in neck-in reduction in order to obtain a stabilized cast film, are desired.
However, EVOH is inferior to polypropylene and polystyrene in thermal stretching properties and as measures therefor, (1) a method of adding a plasticizer to EVOH (for example, see JP-A-53-88067 and JP-A-59-20345) and (2) a method of blending a polyamide resin (for example, see JP-A-52-141785 and JP-A-58-36412) have been suggested. Also, on the other hand, there are also suggested (3) a method of using a resin composition wherein EVOH having a low glass transition temperature, which has relatively favorable stretching properties, is used together (for example, see JP-A-61-4752, JP-A-60-173038, JP-A-63-196645, JP-A-63-230757, JP-A-63-264656, JP-A-2-261847 and JP-A-2000-318095), (4) a method of using an EVOH composition showing a particular crystal melting phenomenon (for example, see JP-A-08-311276) and (5) a method of improving the thermal stretching properties of EVOH at low temperature by adding an ethylene-(meth)acrylic acid copolymer to EVOH (for example, see JP-A-2001-031823) is proposed. Furthermore, studies have been conducted regarding (6) grafting an epoxy compound to EVOH by a melting reaction to improve thermal formability for forming a container and stretching properties (for example, see WO 02/092643 and JP-A-2003-327619).